The present invention relates to a multi-piece golf ball having a core and three or more cover layers. More specifically, the invention relates to a multi-piece solid golf ball which has a high initial velocity on shots taken with a driver and a good spin performance on approach shots.
Numerous golf balls with multilayer covers have hitherto been disclosed. For example, various golf balls with multilayer covers are described in U.S. Pat. Nos. 5,833,553, 6,126,559, 6,220,972, 6,561,928 and 6,309,314. However, these prior-art golf balls do not have a good spin receptivity on approach shots near the green.
A multilayer golf ball is disclosed in U.S. Pat. No. 6,585,608, but this ball has a poor controllability on approach shots.
In the golf balls with multilayer covers disclosed in U.S. Pat. Nos. 5,779,562, 6,117,025, 6,152,834, 6,394,914, 6,213,895 and 6,994,638, the hardness relationships within the multilayer cover have been optimized. Yet, it has been difficult to achieve a sufficiently high initial ball velocity on shots taken with a driver, particularly on shots taken with a driver at a high head speed.
Up until now, golf balls obtained by using a conventional ionomer resin to form the innermost cover layer which directly encases the core have not had a good rebound. To compensate, one known approach has been to reduce the spin rate by increasing the thickness of the inner cover layer made of ionomer resin. Unfortunately, this only lowers the rebound. Moreover, increasing the hardness of the intermediate cover layer so as to increase the rebound has the unfortunate effect of lowering the spin performance on approach shots.
The use of highly neutralized ionomer resins as golf ball cover materials is known to the art, but such covers are relatively thin. Although the golf balls obtained in such cases do have an improved rebound compared with golf balls obtained using prior-art ionomer resins, the spin rate-lowering effect on shots with a driver has been rather negligible.